Enzymatic Janus Liposome Micromotors

Area of Science:

• Materials Science
• Nanotechnology
• Biophysics

Background:

• Designing artificial micro- and nanomotors for directed movement in aqueous environments is a significant challenge.
• Lipid self-assembly offers a versatile platform for creating complex structures with tailored properties.
• Achieving controlled motion often requires asymmetry and localized functionality.

Purpose of the Study:

• To present a novel liposome-based micromotor system capable of autonomous directional motion.
• To demonstrate the use of enzymatic reactions and gas generation for propulsion.
• To investigate the role of Janus configuration and asymmetry in achieving directed movement.

Main Methods:

• Fabrication of Janus liposomes using a mixture of low-melting and high-melting lipids with cholesterol, exploiting lipid liquid-liquid phase separation for stable asymmetry.
• Site-specific enzyme immobilization (horseradish peroxidase) onto one domain of the Janus liposomes via avidin-biotin affinity binding.
• Characterization of liposome motion in the presence of hydrogen peroxide substrate, analyzing factors like substrate concentration and Janus ratio.

Main Results:

• The enzyme-decorated Janus liposomes exhibited directional motion in water, propelled by localized enzymatic conversion and gas generation.
• Observed velocities were significantly higher than Brownian motion, in some cases exceeding it by threefold.
• Experimental parameters such as substrate concentration and the liposome Janus ratio were found to influence motor performance.

Conclusions:

• This study provides a viable method for constructing asymmetrical, lipid-assembled, enzyme-functionalized colloids.
• The findings highlight the critical importance of asymmetry in enabling directed particle motion.
• The developed liposome-based micromotor system demonstrates potential for applications requiring controlled micro-scale transport.